The present invention relates to fluid pumps in general, and more specifically to peristaltic pumps. More particularly, the pump of the invention utilizes at least one occluding roller and at least one pumping roller and can be used in various applications where alternating fluid pumping is needed. Examples of such applications include fluid mixing, single-needle hemodialysis etc.
Peristaltic pumps are well-known devices, which transfer fluid through an elongate flexible tubing by compressing a portion of the tubing, and pushing the fluid through the tubing using such compression. Peristaltic pumps are commonly used for transferring fluids such as ink for printing or for transferring fluids such as blood in medical equipment. Peristaltic pumps may also be used to transfer fluids such as cleaning agents, coolants, slurries or liquid adhesives, just to name a few of the many fluids that can be transferred with such pumps. One advantageous feature of peristaltic pumps is that the fluid does not contact the pump mechanism since the fluid is always confined within and moved through the flexible tubing. Therefore, peristaltic pumps may be used to transfer corrosive or caustic solutions or other hazardous fluids without affecting the pump mechanism.
In a typical peristaltic pump, the tubing is compressed by one or more rollers that are driven by an electric or air-powered motor. Each roller compresses the tubing as it moves along the length of the tubing. Also typically, the flexible tubing is fed through the pump along a generally U-shaped path or alternatively along a substantially straight arc-shaped path (in the case of a pass-through pump) so that the U-shaped or arc-shaped portion of the tubing overlaps a portion of a path traveled by the rollers.
Typical examples of prior art roller pumps may be found in these U.S. Pat. Nos. 5,927,951; 5,630,711; 5,415,532; 4,906,168; and 4,755,168.
Modifications of the classic roller pump configuration is found in the U.S. Pat. No. 5,064,358 describing the design capable of pumping two liquids at the same time. Willock describes a single-needle dialysis system utilizing a roller pump in his U.S. Pat. Nos. 3,938,909 and 3,848,592. Of interest here is the area of application of the roller pump requiring alternating pumping of blood from the patient to the blood dialysis device and back into the patient via the same path.
Such systems are rather complicated and require various valve and control mechanisms to ensure proper redirection of fluid pumping using a standard roller pump. The need exists therefore for a roller pump providing alternating fluid pumping inherently and without changing the direction of rotation or additional external valves and control system.
The need also exists for a roller pump capable of pumping at least two flows independently with a single roller system rotating in the same direction at all times.